Thermostat monitoring system and method

ABSTRACT

A thermostat monitoring method includes measuring an engine coolant temperature with an engine coolant temperature sensor a predetermined amount of time after engine startup, determining with a controller one of four zones to determine whether a thermostat will pass or fail, based on the one of four zones determined, accumulate with the controller one a pass index or a failing index, when the pass index reaches a first threshold, reporting a pass with the controller, and when the failing index reaches a second threshold, reporting a fail with the controller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/611,308 filed on Jun. 1, 2017. The entire disclosure of U.S.patent application Ser. No. 15/611,308 is hereby incorporated herein byreference in its entirety.

BACKGROUND Field of the Invention

The present invention generally relates to a thermostat monitoringsystem and method. More specifically, the present invention relates to athermostat monitoring system and method that detects a thermostatmalfunction or failure.

Background Information

Generally conventional engines include a thermostat to maintain theengine near an optimum operating temperature by regulating the flow ofcoolant to an air-cooled radiator. Various thermostat diagnosticapparatuses have been proposed for diagnosing if a vehicle's thermostatof a cooling system is malfunctioning. Some conventional thermostatdiagnosis system use a model to estimate ECT during the cold start ofthe engine.

SUMMARY

Current regulations require accuracy in the monitoring and diagnosing ofthermostat operations after engine warms up. To meet the new regulationrequirements, a new engine coolant temperature estimation model used tocompare with measured temperatures is needed. It is, however, verydifficult to develop such a model with enough accuracy to robustlydetect thermostat failure without any false detection.

In view of the state of the known technology, one aspect of the presentdisclosure is to provide a thermostat monitoring method, comprisingmeasuring an engine coolant temperature with an engine coolanttemperature sensor a predetermined amount of time after engine startup,determining with a controller one of four zones to determine whether athermostat will pass or fail, based on the one of four zones determined,accumulate with the controller one a pass index or a failing index, whenthe pass index reaches a first threshold, reporting a pass with thecontroller, and when the failing index reaches a second threshold,reporting a fail with the controller.

Another aspect of the present disclosure is related to a thermostatmonitoring method, comprising measuring an engine coolant temperaturewith an engine coolant temperature sensor a predetermined amount of timeafter engine startup, comparing, with a controller, the engine coolanttemperature to determine whether the engine coolant temperature has meta predetermined threshold, when the engine coolant temperature has metthe predetermined threshold, measuring a plurality of engine coolanttemperatures (ECT) with the engine coolant temperature sensor. In oneembodiment the entire monitoring range of ECT is divided into four zonesbased on prescribed temperature thresholds.

The four zones can be Zone 1 (Passing without the Comparison withModel), Zone 2 (Passing with the Comparison with Model), Zone 3 (Failingwithout the Comparison with Model), and Zone 4 (Failing without theComparison with Model). Depending on which zone the current ECT readingbelongs to, the current ECT measurement is compared with a correspondingpredetermined temperature model, or compared with prescribed temperaturethresholds directly, and a passing/failing index is incrementing ordecrementing at variable rates depending on the comparison results, thezone that the current ECT belongs to, and selected engine operatingconditions. Once the passing/failing indices reaches prescribedthreshold, the pass/fail test results can be reported respectively. Inaddition, these indices could also be reset to 0 when the current enginecoolant temperature crosses a prescribed threshold, or test is completed(pass or fail). The thermostat monitor, therefore, can run continuouslythroughout the driving cycle after it is enabled.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a schematic view of the engine cooling system;

FIG. 2 is an enlarged view of a thermostat for the engine cooling systemof FIG. 1 in a closed position;

FIG. 3 is an enlarged view of a thermostat for the engine cooling systemof FIG. 1 in an open position;

FIG. 4 is a schematic of a thermostat monitoring system according to anembodiment of the present invention;

FIG. 5 is chart illustrating the four pass/fail zones;

FIG. 6 is a graph illustrating an example of enabling the after warm-upcontinuous thermostat monitoring after the actual engine coolanttemperature is above the estimated temperature during engine warming up(i.e., no fault is detected during the warm-up test);

FIG. 7 is a graph illustrating an example of enabling the after warm-upcontinuous thermostat monitor after the actual engine coolanttemperature is below the estimated temperature during engine warming upand no fault is set (i.e., there is no judgement during the warm-uptest);

FIG. 8 is a graph illustrating an example of enabling the after warm-upcontinuous thermostat monitor after the engine start right after a shortperiod of (i.e, there is no warm-up test in the beginning of the drivingcycle)soak time;

FIG. 9 illustrates a chart indicating different scenarios of the passingindex increment for a thermostat monitor;

FIG. 10 illustrates another chart indicating the different scenarios ofthe passing index increment for a thermostat monitor when there is anexisting thermostat failure;

FIG. 11 illustrates another chart indicating different scenarios of thefailing index increment for a thermostat monitor;

FIG. 12A-C is a flow chart illustrating the process to determine whetherthe thermostat has passed the diagnosis process;

FIG. 13 is a flow chart illustrating the process of the accumulation ofthe passing index without pending of confirmed fault in Zone 1;

FIG. 14 is a flow chart illustrating the process of the accumulation ofthe passing index with a pending or confirmed fault in Zone 1;

FIG. 15 is a flow chart illustrating the process of the accumulation ofthe passing index without pending of confirmed fault in Zone 2;

FIG. 16A is a flow chart illustrating the process of the accumulation ofthe passing index with a pending or confirmed fault in Zone 2;

FIG. 16B is a flow chart illustrating a second embodiment for theprocess of the accumulation of the passing index with a pending orconfirmed fault in Zone 2;

FIG. 17 is a flow chart illustrating the process of the accumulation ofthe failing index in Zone 4;

FIG. 18A is a flow chart illustrating the process of the accumulation ofthe failing index in Zone 3; and

FIG. 18B is a flow chart illustrating a second process of theaccumulation of the failing index in Zone 3.

DETAILED DESCRIPTION OF EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the art from thisdisclosure that the following descriptions of the embodiments areprovided for illustration only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

Referring initially to FIGS. 1-4, an engine thermostat monitoring system10 is illustrated in accordance with a first embodiment. As can be seen,the engine thermostat monitoring system 10 includes a sensor 12, acontroller 14, a display device 16 and a storage device 18 and monitorsa thermostat 20 in an engine cooling system 22, generally of a vehicle,by monitoring the engine coolant temperature (ECT). The engine coolingsystem cools the engine E and includes a radiator 24, a water pump 26, aheater core 28, a heater control valve 30 and an expansion tank 32.

The engine E can operate at around 200 degrees F. At cold start up, theengine temperature is below this operating temperature and generallyrequires more fuel to run properly. Thus, as shown in FIG. 2, when theengine is cold the thermostat 20 blocks flow of the coolant to theradiator and opens the bypass circuit. In this mode the water pump 26circulates coolant only inside the engine E. The coolant is preventedfrom flowing through the radiator 24 where it would be cooled. Insteadcoolant flows through the bypass and back to the water pump 26. Theeffect is a quick increase in engine temperature.

The thermostat 20 can be a temperature controlled valve. The spring 34loaded valve is attached to a small cylinder 36 filled with thermal wax.As shown in FIG. 3, when the engine warms up, coolant transfers heat tothe wax-filled cylinder 36. The heat causes the cylinder 36 to expandand pushes down on the spring 34 loaded valve. The water pump 26 nowpushes coolant through the cylinder head and out to the radiator 24,where the heat is removed. Lower temperature coolant leaves the radiator24 and circulates back to the water pump 26 completing the cycle. If thetemperature begins to fall below the limit set by the thermostat 20 theflow will be restricted until it rises to the proper level.

As coolant ages, the additives that prevent corrosion are depleted. Thiscauses damage to the thermostat 20 and can cause the thermostat 20 tostick. If the thermostat 20 sticks open, the engine E runs too cold andwastes fuel. When the thermostat 20 sticks closed the engine E willoverheat. Overheating causes cylinder heads in the engine E to expandgreatly. This has the effect of crushing the cylinder head gasket whichcan crack the cylinder heads. Pistons in the engine E also expand andgall the cylinder walls. Overheating, even for a short while canseverely damage the engine E.

The present engine thermostat monitoring system 10 monitors the statusand operation of the thermostat 20 and accurately determines whetheroperation is within an acceptable rage.

The controller 14 for the engine thermostat monitoring system 10 can beany suitable controller 14, and in one embodiment can be an enginecontrol unit (ECU). The controller 14 is operatively connected to thesensor 12 (e.g., an engine coolant sensor 12), a display device 16 andthe storage device 18. The controller 14 can include a microcomputerwith a control program that controls the sensor 12, the display device16 and the storage device 18 as discussed below. The controller 14 canalso include other conventional components such as an input interfacecircuit, an output interface circuit, and storage device 18 s such as aROM (Read Only Memory) device and a RAM (Random Access Memory) device.The microcomputer of the controller 14 is programmed to control thesensor 12 and the storage device 18. The memory circuit storesprocessing results and control programs such as ones for the sensor 12,the display device 16 and the storage device 18 operation that are runby the processor circuit. The controller 14 is operatively coupled tothe sensor 12, the display device 16 and the storage device 18 in aconventional manner. The internal RAM of the controller 14 storesstatuses of operational flags and various control data. The controller14 is capable of selectively controlling any of the components of theengine thermostat monitoring system 10 (or any other desired aspect) inaccordance with the control program. It will be apparent to thoseskilled in the art from this disclosure that the precise structure andalgorithms for the controller 14 can be any combination of hardware andsoftware that will carry out the functions of the present invention.

The sensor 12 can be any suitable engine coolant temperature sensor (ECTsensor 12), and measures the temperature of the engine coolant of anengine (e.g. an internal combustion engine). The readings from thissensor 12 are then fed back to the controller 14 for control purposes.

The display device 16 can be any suitable display device. For example,the display device 16 can be a light or a warning within the vehicle,such as a check engine light a warning light an auditory sound or anyother suitable notification system. Alternatively, the display device 16can be on a remote device that is wirelessly or directly wired to thesystem 10 to check the engine operating status. Accordingly, in any ofthe embodiments described herein, when a pass or a fail is determined,such an indication can be displayed on the display device 16.

The present system 10 is a continuously-running thermostat monitoringsystem that improves monitoring and determination of failure of thethermostat 20. The embodiments discussed herein are based on a four-zonepassing/failing system for thermostat malfunction detection. Based onpossible regulation requirements and thermostat monitoring needs, theECT operating range is divided into four zones for thermostat faultdetection. Each zone is separated from another zone by a predeterminedtemperature. As shown in FIG. 5, when the ECT is greater than or equalto the second predetermined temperature, such ECT operating zone is thethermostat monitoring “Passing Zone without Model” (Zone 1). That is tosay, the increment of passing index in this zone is independent of anassociated ECT model estimation. In other words, the model orpredetermined model, as used herein, is a predicted temperature, atwhich the ECT is predicted based on various factors in variables of theengine at predetermined times to establish a predetermined model orpredetermined temperature model that is stored in a storage device(e.g., storage device 18). The controller has access to thepredetermined model, and as discussed herein can compare the actual ECTto the predetermined model.

When the ECT is greater and or equal to the first predeterminedtemperature and less than the second predetermined temperature, the ECToperating zone is the thermostat monitoring “Passing Zone with Model”(Zone 2). That is, the increment of passing index in this zone relies onthe associated ECT model estimation.

When the ECT is greater and or equal to the third predeterminedtemperature and less than the first predetermined temperature, the ECToperating zone is the thermostat monitoring “Failing Zone with Model”(Zone 3).

When the ECT is less than the third predetermined temperature, the ECToperating zone is the thermostat monitoring “Failing Zone without Model”(Zone 4).

FIG. 6 illustrates the temperature and time requirements after engine iswarmed up for a faulty thermostat. In the embodiment, the firstpredetermined temperature (Temp i) of the ECT is 70 degrees C., and thesecond predetermined temperature (Temp ii) of the ECT is 75 degrees C.As the engine E warms up for cold start, the actual ECT increases at arate that is faster than expected based on the predicated model or theestimated temperature. In this embodiment, a diagnosis takes place atthe start up and ends at a first predetermined time. As shown, thethermostat 20 could be determined to have failed in an initial diagnosisprior to reaching the predetermined time. However, in this embodiment ofthe present invention, the continuous diagnosis takes place afterreaching the second predetermined temperature. Thus, as stated above,the monitoring and diagnosis of the thermostat 20 can occur continuouslyduring engine run and is more accurate.

As shown in FIG. 7, in the present embodiment, the thermostat monitoringalgorithm is always enabled after ECT reaches second predeterminedtemperature (Temp ii) for the first time—based on a reading from thesensor 12, and there is no previous fault for thermostat warmupdiagnosis. In this embodiment, it can be seen that the actual ECT isdelayed relative to the predicated model or the estimated temperature,and the actual ECT does not reach the second predetermined temperature(temp ii) at the predetermined time. As illustrated, the system 10 candetermine that the thermostat 20 has failed since the actual ECT failedto reach the second predetermined temperature within the predeterminedtime. However, in this embodiment, the continuous diagnosis can beginafter the actual ECT reaches the second predetermined temperature at thesecond time. Such a system 10 can result in a more accurate diagnosis ofthe thermostat 20. However, it is noted that diagnosis may not occur(e.g., remain disabled) if the actual ECT does not reach secondpredetermined temperature (Temp ii) or if there is a previous fault inthe thermostat warmup diagnosis.

FIG. 8 illustrates another embodiment in which the system 10 determineswhether the thermostat 20 can pass after a sort soak time. In thisembodiment, it can be seen that the temperature reaches the secondpredetermined temperature (temp ii—e.g. 75 degrees C.) relativelyquickly. It is noted that in this embodiment, the system detects whetherthe thermostat is open such that the ECT can drop below the firstpredetermined temperature (Temp. ii) during normal driving conditions.

As shown in FIG. 9, illustrates three cases in which a pass/faildetermination is made after it has been determined that the warm testhas been passed and there are no previous fail determinations, as shownin FIG. 8. In this embodiment, the controller 14 is programmed to add orsubtract variable increment steps of the passing index in the passingzone without model and the passing zone with model. Such a system 10reduces the dependency on model, and improve the robustness of passing.The ratio between the increment step in the passing zone without modeland that in the passing zone with model is adjustable based on theaccuracy of the model. The less accurate the model is, the high ratiobetween the two step increments are.

Case 1 illustrates a passing situation without use of the model (Zone1). As shown in FIG. 9, when the actual ECT is greater than or equal tothe second predetermined temperature (Temp ii) the system 10 using thepassing zone without the model. In this passing zone, the passing indexis incremented by a predetermined number step, (e.g., 5), regardless ofthe estimation value from model. Once the passing timer crosses athreshold, a pass can be reported and numerator is incremented by 1.

Case 2 illustrates a passing situation with the model (Zone 2). As shownin FIG. 9, when the actual ECT is less than the second predeterminedtemperature (Temp ii), but greater than the first predeterminedtemperature, the system 10 utilizes the passing zone with the model.That is, the controller 14 compares the actual ECT with a predeterminedmodel, based on any suitable engine variables and/or factors. In thisembodiment, the passing index will increment by a predetermined numberstep_(β) (e.g., 1). In this embodiment, the passing index can hold itsvalue if the actual ECT is less than the model and the passing index isnon-zero.

Case 3 illustrates a failing situation with the model (Zone 2). As shownin FIG. 9, when the actual ECT is less than a first predeterminedtemperature (Temp i, e.g., 70 degrees C.), the controller 14 comparesthe actual ECT with the predetermined model, based on any suitableengine variables and/or factors. In this embodiment, when the actual ECTis below the first predetermined temperature (Temp i) and below thepredetermined model, the passing index will reset to 0, a fail isreported and the passing index is reset to zero. The fail can bedisplayed on the display device 16.

FIG. 10 illustrates, illustrates three cases in which a pass/faildetermination has been made after it has been determined that the warmtest has been passed and there is previous fail determination (i.e., apending or confirmed thermostat fault). In this embodiment, additionalrestrictions are set to increment the passing index in the passing zonewithout model. Such restrictions result in robustness for not clearingthe pending/confirmed fault and increasing the chance to duplicate thefault when there is a pending fault

Preferably, in one embodiment the controller 14 enables the passingindex to increase when the actual ECT is greater than the predeterminedmodel, and reduce when actual ECT is less than the predetermined model.Such an embodiment increases the robustness of the passing algorithm inthe zone with model. However, if desired, in the passing zone with modelthe controller 14 can stop and hold the passing index. Accordingly, insuch an embodiment, the passing index can only increase in the passingzone without model.

Case 1 illustrates a passing situation without use of the model (Zone1). As shown in FIG. 10, when the actual ECT is greater than or equal tothe second predetermined temperature (Temp ii) the system 10 using thepassing zone without the model. In this passing zone, the passing indexis incremented by a predetermined number step_(α) (e.g., 5), when theengine load is less than or equal to a predetermined engine threshold(e.g., 30%) and when the vehicle is at or above a predetermined vehiclespeed (e.g., greater and or equal to 20 MPH). Once the passing timercrosses a threshold, a pass can be reported and numerator is incrementedby 1, and the previous once the passing index crosses a predeterminedthreshold, a pass can be reported, and the pending or confirmedthermostat fault can be cleared, and numerator is incremented by 1.

Case 2 illustrates a passing situation with the model (Zone 2). As shownin FIG. 10, when the actual ECT is less than the second predeterminedtemperature (Temp ii), but greater than the first predeterminedtemperature, the system 10 utilizes the passing zone with the model.That is, the controller 14 compares the actual ECT with a predeterminedmodel, based on any suitable engine variables and/or factors. In thisembodiment, the passing index will increment by a predetermined numberstep_(β) (e.g., 1) if the actual ECT is greater than the predeterminemodel and the failing index is 0. In Example 1, the passing index willhold its value if the actual ECT is less than the predetermined modeland the passing index is non-zero. Alternatively, in Example 2, thepassing index can be reduced by 0.2 if the actual ECT is less than thepredetermined model until the passing index reaches 0, when the passingindex is non-zero. Once the passing index crosses a predeterminedthreshold, a pass can be reported, and the pending or confirmedthermostat fault can be cleared, and numerator is incremented by 1.

Case 3 illustrates a failing situation with the model (Zone 3). As shownin FIG. 10, When the actual ECT is less than the first predeterminedtemperature (Temp i), the controller 14 compares the actual ECT with thepredetermined model, based on any suitable engine variables and/orfactors. In this embodiment, when the actual ECT is below the firstpredetermined temperature (Temp i) and below the predetermined model,the passing index will reset to 0, a fail is reported and the passingindex is reset to zero.

FIG. 11 illustrates an embodiment in which restrictions are added toincrement a failing index in the failing zone without model (Zone 4).Such an embodiment enables avoids noise factors that cause the ECT todrop during low load conditions. In one embodiment, in the failing zonewith model, the failing index is incremented only when predeterminedmodel is greater than or equal to the first predetermined temperature(Temp i). In another embodiment, the failing index increment rate variesbased on when the actual ECT is greater than or equal to thepredetermined model, the actual ECT is less than the predeterminedmodel, and the actual ECT is less than the first predeterminedtemperature (Temp i), and the first predetermined temperature (Temp i)is less than or equal to the predetermined model. Such an embodimentincreases the robustness of the fault detection and minimizes the impactfrom transient noise factors.

Thus, as shown in FIG. 11, when the failing index is greater than zeroand the actual ECT is in the failing zone with model (Zone 3) (i.e.,less than Temp(i)), the failing index remains the same when the ECT isless than the predetermined model and decreases by a calibratable stepwhen the ECT is greater than or equal to the predetermined model. Thefailing index can be reset when the actual ECT is greater than thesecond predetermined temperature (Temp ii).

Thus, as shown in FIG. 11, when the actual ECT is less than the thirdpredetermined temperature (Temp iii) (Temp(iii) is a new temp line belowTemp i), the failing index can be incremented by steps' (e.g., 10),regardless of the predetermined value. If desired, in one embodiment,the failing index can vary based on the engine load (over 30%) andactual ECT.

Moreover, as illustrated in FIG. 11, in Example 3, when the actual ECTis less than the first predetermined temperature (Temp i), the failingindex can be incremented by a predetermined step_(β2) (e.g., 3) when thepredetermined model is greater and the third predetermined temperature(Temp iii). The failing index can be held and there is no judgement forother temperature situations.

Alternatively, in Example 4 the failing index can be incremented bystep_(β2) (e.g., 3) when the actual ECT is less than the thirdpredetermined temperature (Temp iii) and predetermined model is greaterand the third predetermined temperature (Temp iii), the failing indexcan be incremented by step_(ζ1) (e.g., 1) when the actual ECT is greaterthan the predetermined and the engine load, which is in turn greaterthan or equal to a threshold E, and predetermined vehicle speedconditions exists, such an increment can be calibratable, and preventsan actual ECT that is larger than the predetermined model due to a modelaccuracy issue. Further, the failing index can be incremented bystep_(β2) (e.g., 2), when the actual ECT is less than the predeterminedmodel and the predetermined model is less than the third predeterminedtemperature (Temp i). In these embodiment, a failure can be reported andset when the failing index crosses a threshold F

As shown in FIG. 11, when the actual ECT is greater than or equal to thefirst predetermined temperature (Temp i), and less than the secondpredetermined temperature (Temp ii) (Zone 2), the failing index willhold when the actual ECT is less than the predetermined model and thefailing index is greater and zero. Additionally, the failing index willdecrease by stem (e.g., 1) when the actual ECT is greater than thepredetermined model when the failing index is greater than zero 0. Whenthe actual ECT is greater than the second predetermined temperature(Temp ii), the failing index will be reset to 0.

Embodiments of the present invention cause the diagnostic algorithm torun continuously when passing, and stop the algorithm after a failureand latch it for the rest of the key cycle (robustness against noisefactors after fault detection and save ECU resources). The diagnostic isre-enabled in a new key cycle. After the pass index crosses theprescribed threshold, a pass will be reported to clear pending/confirmedfault (Diagnostic Trouble Code), if any. Additionally, the controller 14will reset the passing index and other testing parameters associatedwith the past passing test to force the monitoring to restart. Once afault is detected (the failing index crosses the prescribed threshold),the diagnostic algorithm will be latched to test complete status for therest of the driving cycle. All diagnostic testing related parameters arereset at keyon such that the diagnostic could be re-enabled once ECTcrosses the second predetermined temperature (Temp ii) for the 1^(st)time in that key cycle.

FIGS. 12A-C illustrate a flow chart for the procedure of one embodimentof the present invention. First in step S100 the controller 14 isprogrammed to determine whether the thermostat monitor fails in astandard existing driving cycle. If the thermostat monitors fails inthis cycle, the controller, in step S110, can determine that there is noneed to enable the after warm-up monitor in the current driving cycleand ends the current loop.

If the controller 14 determines that the thermostat monitors does notfail in this cycle (i.e., warm-up monitor passes or no judgement is madeor the warm-up monitor is not enabled), the controller, in step S120,causes the current ECT reading to be obtained.

The controller then moves to temperature zone selection. The controller14 determines whether the current ECT temperature reading is within the“passing zone without model” (Zone 1) in step S130. In other words, isthe ECT greater than the second predetermined temperature (Temp ii)? Ifthe controller 14 determines that the ECT is less than the secondpredetermined temperature (Temp ii), in step S140, the controller 14determines whether the current reading is in the “passing zone withmodel” (Zone 2). That is, the controller 14 determines whether the ECTreading is greater than or equal to the first predetermined temperature(Temp i) and greater than or equal to the second predeterminedtemperature (Temp ii). In other words, is the ECT greater than the firstpredetermined temperature (Temp i)?

If the controller 14 determines that the ECT is less than the firstpredetermined temperature (Temp i), in step S150, the controller 14determines whether the current reading is in the “failing zone withmodel” (Zone 3). That is, the controller 14 determines whether the ECTreading is greater than or equal to the third predetermined temperature(Temp iiii) and greater than or equal to the first predeterminedtemperature (Temp i). In other words, is the ECT greater than the thirdpredetermined temperature (Temp iii)?

If the controller 14 determines that the ECT is less than the thirdpredetermined temperature (Temp iii), the controller 14 determines thatthe current reading is in Zone 4 (i.e., failing zone without model) andresets the passing index to 0 in step S160. The controller thenaccumulates the failing index in Zone 4 in step S170. The controller 14then determines whether the failing index crosses threshold B in stepS180. If the failing index crosses threshold B, a fail is reported instep S190 and the current loop is ended. If the failing index does notcross threshold B in step S180, the current loop is ended.

Turning back to step S150, if the controller 14 determines that the ECTis greater than or equal to the third predetermined temperature (Tempiii), the controller 14 determines that the current reading is in Zone 3(i.e., failing zone with model). The controller 14 then accumulates thefailing index in Zone 3 in step S200. The controller 14 then determineswhether the failing index crosses threshold B in step S180. If thefailing index crosses threshold B, a fail is reported in step S190 andthe current loop is ended. If the failing index does not cross thresholdB in step S180, the current loop is ended.

Turning back to step S130, if the controller 14 determines the ECTreading to greater than second predetermined temperature (Temp ii), thecontroller 14 resets the failing index to 0 in step S210. The controller14 then determines the existing thermostat rationality fault (i.e., isthere a fault confirmed or pending) in step S220. If there is a faultconfirmed or pending, the controller 14, in step S230 accumulates thepassing index with a pending or confirmed fault in Zone 1. Thecontroller 14 in step S240 then determines whether the passing indexcrosses the threshold A. If the passing index crosses the threshold A, apass is reported and the fault is cleared (if any) in step S250, thecurrent loop is then ended. If the passing index does not cross thethreshold A, the current loop is then ended.

Turning back to step S220, if there is no fault confirmed or pending,the controller 14, in step S260 accumulates the passing index without apending or confirmed fault in Zone 1. The controller 14 in step S240then determines whether the passing index crosses the threshold A. Ifthe passing index crosses the threshold A, a pass is reported and thefault is cleared (if any) in step S250, the current loop is then ended.If the passing index does not cross the threshold A, the current loop isthen ended.

Turning back to step S140, if the controller 14 determines the ECTreading to greater than first predetermined temperature (Temp i) andless than or equal to the second predetermined temperature (Temp ii),the controller 14 then determines the existing thermostat rationalityfault (i.e., is there a fault confirmed or pending) in step S270. Ifthere is a fault confirmed or pending, the controller 14, in step S280accumulates the passing index with a pending or confirmed fault in Zone2. The controller 14 in step S240 then determines whether the passingindex crosses the threshold A. If the passing index crosses thethreshold A, a pass is reported and the fault is cleared (if any) instep S250, the current loop is then ended. If the passing index does notcross the threshold A, the current loop is then ended.

Turning back to step S270, if there is no fault confirmed or pending,the controller 14, in step S290 accumulates the passing index without apending or confirmed fault in Zone 2. The controller 14 in step S240then determines whether the passing index crosses the threshold A. Ifthe passing index crosses the threshold A, a pass is reported and thefault is cleared (if any) in step S250, the current loop is then ended.If the passing index does not cross the threshold A, the current loop isthen ended.

FIG. 13 is a flow chart illustrating the process of the accumulation ofthe passing index without pending of confirmed fault in Zone 1, i.e.,step S260. First in step 260A, the controller 14 determines whether theECT reading is in Zone 1. If the ECT reading is in Zone 1, thecontroller 14 determines whether the passing index crosses a thresholdin step S260B. If the threshold has not been passed, in step S260C, thepassing index is increased by plus one step, and the current loop isended. If the passing index does cross a threshold, a pass is reportedin step S260D and the failing and/or passing index is reset, and thecurrent loop is ended. If in step S260A, the ECT reading is not in Zone1, the controller 14 determines whether the ECT reading is in Zone 4 instep S260E. If the ECT reading is not in Zone 4, the current loop isended. If the ECT reading is in Zone 4, the controller 14 resets thepassing index in S260F and the current loop is ended.

FIG. 14 is a flow chart illustrating the process of the accumulation ofthe passing index with a pending or confirmed fault in Zone 1, i.e.,step S230. First in step 230A, the controller 14 determines whether theECT reading is in Zone 1. If the ECT reading is in Zone 1, thecontroller 14 determines whether the passing index crosses a thresholdin step S230B. If the threshold has not been passed, in step S260C, thecontroller 14 determines whether the vehicle speed is greater than orequal to a threshold and/or whether the engine load is less than orequal to a threshold. If the vehicle speed is greater than or equal to athreshold and/or whether the engine load is less than or equal to athreshold, the passing index is increased by plus one step in stepS230D. If the vehicle speed is not greater than or equal to a thresholdand/or the engine load is not less than or equal to a threshold, thepassing index is held in step 230E and the current loop is ended. If thepassing index does cross a threshold, a pass is reported in step S230Fand the failing and/or passing index is reset, and the current loop isended. If in step S230A, the ECT reading is not in Zone 1, thecontroller 14 determines whether the ECT reading is in Zone 4 in stepS230G. If the ECT reading is not in Zone 4, the current loop is ended.If the ECT reading is in Zone 4, the controller 14 resets the passingindex in S260H and the current loop is ended.

FIG. 15 is a flow chart illustrating the process of the accumulation ofthe passing index without pending of confirmed fault in Zone 2, i.e.,step S290. First in step 290A, the controller 14 determines whether theECT reading is in Zone 2. If the ECT reading is in Zone 2, thecontroller 14 determines whether the passing index crosses a thresholdin step S290B. If the threshold has not been passed, in step S290C, thecontroller 14 compares the ECT reading (the measured ECT) to theestimated ECT (the ECT from a predetermined model). If the measured ECTis greater than or equal to the estimated ECT, the passing index isincreased by a predetermined step in step S290D, and the current loop isended. If the measured ECT is less than the estimated ECT, the passingindex is held in step S290E, and the current loop is ended. If thepassing index does cross a threshold, a pass is reported in step S260Fand the failing and/or passing index is reset, and the current loop isended. If in step S260A, the ECT reading is not in Zone 1, thecontroller 14 determines whether the ECT reading is in Zone 4 in stepS260G. If the ECT reading is not in Zone 4, the current loop is ended.If the ECT reading is in Zone 4, the controller 14 resets the passingindex in S260H and the current loop is ended.

FIG. 16A is a flow chart illustrating the process of the accumulation ofthe passing index with a pending or confirmed fault in Zone 2, i.e.,step S280. First in step 280A, the controller 14 determines whether theECT reading is in Zone 2. If the ECT reading is in Zone 2, thecontroller 14 determines whether the passing index crosses a thresholdin step S280B. If the threshold has not been passed, the controller 14compares the ECT reading (the measured ECT) to the estimated ECT (theECT from a predetermined model) in step S280C. If the measured ECT isgreater than or equal to the estimated ECT, the passing index isincreased by a predetermined step in step S280D, and the current loop isended. If the measured ECT is less than the estimated ECT, the passingindex is held in step S280E, and the current loop is ended. If thepassing index does cross a threshold in step S280B, a pass is reportedin step S280F and the failing and/or passing index is reset, and thecurrent loop is ended. If in step S280A, the ECT reading is not in Zone2, the controller 14 determines whether the ECT reading is in Zone 4 instep S280G. If the ECT reading is not in Zone 4, the current loop isended. If the ECT reading is in Zone 4, the controller 14 resets thepassing index in S260H and the current loop is ended.

FIG. 16B is a flow chart illustrating a second embodiment for theprocess of the accumulation of the passing index with a pending orconfirmed fault in Zone 2, i.e., step S280. First in step 2801, thecontroller 14 determines whether the ECT reading is in Zone 2. If theECT reading is in Zone 2, the controller 14 determines whether thepassing index crosses a threshold in step S280J. If the threshold hasnot been passed, the controller 14 compares the ECT reading (themeasured ECT) to the estimated ECT (the ECT from a predetermined model)in step S280K. If the measured ECT is greater than or equal to theestimated ECT, the passing index is increased by a predetermined step instep S280L, and the current loop is ended. If the measured ECT is lessthan the estimated ECT, the controller 14 determines whether the passindex is greater than 0 in step S280M. if the passing index is notgreater than 0, the current loop is ended. If the passing index isgreater than zero, the passing index is reduced by a predetermined index(e.g., step 3) in step S280N, and the current loop is ended. If thepassing index does cross a threshold in step S280J, a pass is reportedin step S280P and the failing and/or passing index is reset, and thecurrent loop is ended. If in step S2801, the ECT reading is not in Zone2, the controller 14 determines whether the ECT reading is in Zone 4 instep S280R. If the ECT reading is not in Zone 4, the current loop isended. If the ECT reading is in Zone 4, the controller 14 resets thepassing index in S260T and the current loop is ended.

FIG. 17 is a flow chart illustrating the process of the accumulation ofthe failing index in Zone 4, i.e., step S170. First in step 170A, thecontroller 14 determines whether the ECT reading is in Zone 4. If theECT reading is in Zone 4, the controller 14 determines whether thepassing index crosses a threshold in step S170B. If the threshold hasnot been crossed, in step S170C, the controller 14 determines whetherthe vehicle speed is less than or equal to a threshold and/or optionallywhether the engine load is greater than or equal to a threshold. If thevehicle speed is less than or equal to a threshold and/or the engineload is greater than or equal to the threshold, the passing index isincreased by a predetermined step in step S170D. If the vehicle speed isgreater than or equal to a threshold and/or the engine load is not lessthan or equal to a threshold, the passing index is held in step S170Eand the current loop is ended. If the passing index does cross athreshold, a fail is reported in step S170F and the failing and/orpassing index is reset, and the current loop is ended. If in step S170A,the ECT reading is not in Zone 4, the controller 14 determines whetherthe ECT reading is in Zone 1 in step S170G. If the ECT reading is not inZone 1, the current loop is ended. If the ECT reading is in Zone 1, thecontroller 14 resets the passing index in S170H and the current loop isended.

FIG. 18A is a flow chart illustrating the process of the accumulation ofthe failing index in Zone 3, i.e., step S200. First in step 200A, thecontroller 14 determines whether the ECT reading is in Zone 3. If theECT reading is in Zone 3, the controller 14 determines whether thepassing index crosses a threshold in step S200B. If the threshold hasnot been crossed, in step S200C, the controller 14 determines whetherthe ECT reading (measured ECT) is less than a regulated threshold toenable other diagnostics (e.g., is Temp i less than the estimated temp).If the ECT reading (measured ECT) is less than a regulated threshold,the failing index is increased by a predetermined step in step S200D. Ifthe ECT reading (measured ECT) is less than a regulated threshold, thepassing index is held in step S200E and the current loop is ended. Ifthe passing index does cross a threshold, a fail is reported in stepS200F and the failing and/or passing index is reset, and the currentloop is ended. If in step S200A, the ECT reading is not in Zone 3, thecontroller 14 determines whether the ECT reading is in Zone 1 in stepS200G. If the ECT reading is not in Zone 1, the current loop is ended.If the ECT reading is in Zone 1, the controller 14 resets the passingindex in S200H and the current loop is ended.

FIG. 18B is a flow chart illustrating a second process of theaccumulation of the failing index in Zone 3, i.e., step S200. First instep 2001, the controller 14 determines whether the ECT reading is inZone 3. If the ECT reading is in Zone 3, the controller 14 determineswhether the passing index crosses a threshold in step S200J. If thethreshold has not been crossed, in step S200J, the controller 14determines whether the ECT reading (measured ECT) is less than aregulated threshold to enable other diagnostics (e.g., is Temp i lessthan the estimated temp) in step S200K. If the ECT reading (measuredECT) is less than a regulated threshold, the failing index is increasedby a predetermined step in step S200L and the current loop is ended. Ifthe ECT reading (measured ECT) is less than a regulated threshold, thecontroller 14 determines whether the ECT reading (measured ECT) is lessthan or equal to the first predetermined temperature and less than anestimated (model ECT) in step S200M. If the ECT reading (measured ECT)is less than or equal to the first predetermined temperature and lessthan an estimated (model ECT) the failing index is incremented by apredetermined amount in step S200N, and the current loop is ended. Ifthe ECT reading (measured ECT) is not less than or equal to the firstpredetermined temperature and not less than an estimated (model ECT),the controller 14 determines whether the ECT reading is less than thefirst predetermined temperature and whether a vehicle speed and lessthan or equal to a speed threshold and whether the engine load is lessthan or equal to a load threshold, in step S200P. If the ECT reading isless than the first predetermined temperature and a vehicle speed isless than or equal to a speed threshold and the engine load is less thanor equal to a load threshold, the failing index is increased by apredetermined amount in step S200R and the current loop is ended. If theECT reading is not less than the first predetermined temperature and thevehicle speed is not less than or equal to the speed threshold and theengine load is not less than or equal to a load threshold, thecontroller 14 determines whether the ECT reading is greater than theestimated (model) ECT and whether the failing index is greater than 0 instep S200S. If the ECT reading is greater than the estimated (model) ECTand the failing index is greater than 0, the failing index is decreasedby a predetermined step (a decrease in the failing index) in step S200Tand the current loop is ended. If the ECT reading is not greater thanthe estimated (model) ECT and the failing index is not greater than 0,the failing index is held in step S200U. If the passing index does crossa threshold, a fail is reported in step S200V and the failing and/orpassing index is reset, and the current loop is ended. If in step S200H,the ECT reading is not in Zone 3, the controller 14 determines whetherthe ECT reading is in Zone 1 in step S200W. If the ECT reading is not inZone 1, the current loop is ended. If the ECT reading is in Zone 1, thecontroller 14 resets the passing index in S200X and the current loop isended.

The sensor 12, the thermostat 20 and the display device 16 areconventional components that are well known in the art. Since exhaustsensor 12, the thermostat 20 and the display device 16 are well known inthe art, these structures will not be discussed or illustrated in detailherein. Rather, it will be apparent to those skilled in the art fromthis disclosure that the components can be any type of structure and/orprogramming that can be used to carry out the present invention.

GENERAL INTERPRETATION OF TERMS

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part” or “element” when used in thesingular can have the dual meaning of a single part or a plurality ofparts. Also as used herein to describe the above embodiment(s), thefollowing directional terms “above”, “downward”, and “below” as well asany other similar directional terms refer to those directions of avehicle equipped with the thermostat monitoring system 10 and method.

Accordingly, these terms, as utilized to describe the present inventionshould be interpreted relative to a vehicle equipped with the thermostatmonitoring system 10 and method.

The term “detect” as used herein to describe an operation or functioncarried out by a component, a section, a device or the like includes acomponent, a device or the like that does not require physicaldetection, but rather includes determining, measuring, modeling,predicting or computing or the like to carry out the operation orfunction.

The term “configured” as used herein to describe a component, section orpart of a device includes hardware and/or software that is constructedand/or programmed to carry out the desired function.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. For example, the size, shape, location ororientation of the various components can be changed as needed and/ordesired. Components that are shown directly connected or contacting eachother can have intermediate structures disposed between them. Thefunctions of one element can be performed by two, and vice versa. Thestructures and functions of one embodiment can be adopted in anotherembodiment. It is not necessary for all advantages to be present in aparticular embodiment at the same time. Every feature which is uniquefrom the prior art, alone or in combination with other features, alsoshould be considered a separate description of further inventions by theapplicant, including the structural and/or functional concepts embodiedby such feature(s). Thus, the foregoing descriptions of the embodimentsaccording to the present invention are provided for illustration only,and not for the purpose of limiting the invention as defined by theappended claims and their equivalents.

What is claimed is:
 1. A thermostat monitoring method, comprising: measuring an engine coolant temperature with an engine coolant temperature sensor a predetermined amount of time after engine startup; determining with a controller one of four zones to determine whether a thermostat will pass or fail; based on the one of four zones determined, accumulate with the controller one a pass index or a failing index; when the pass index reaches a first threshold, reporting a pass with the controller; and when the failing index reaches a second threshold, reporting a fail with the controller.
 2. The method of claim 1, further comprising comparing the measure engine coolant temperature with an estimated engine coolant temperature.
 3. The method of claim 3, further comprising comparing the engine speed with a threshold engine speed.
 4. The method of claim 3, further comprising comparing the engine load with a threshold engine load.
 5. The method of claim 1, further comprising determining with the controller whether the thermostat has failed previously.
 6. The method of claim 1, wherein when the controller has determined that the thermostat has failed previously the passing index is increased by a first increment.
 7. The method of claim 6, wherein when the controller has determined that the thermostat has not failed previously the passing index is increased by a second increment, the second increment being different from the first increment.
 8. The method of claim 1, further comprising resetting a pass/fail counter.
 9. The method of claim 1, further comprising incrementing the failing index only when a predetermined model is greater than or equal to the engine coolant temperature.
 10. The method of claim 1, further comprising incrementing the failing index by a predetermined amount when the engine coolant temperature is less than a predetermined temperature.
 11. The method of claim 1, further comprising incrementing the passing index by a predetermined number when the engine coolant temperature is greater than a predetermine model and the failing index is
 0. 12. The method of claim 1, further comprising varying the failing index can vary based on engine load.
 13. The method of claim 1, further comprising incrementing the failing index by a predetermined number when the engine coolant temperature is less than a predetermined model and the predetermined model is less than a predetermined temperature.
 14. The method of claim 1, further comprising decreasing the failing index by a predetermined number when the engine coolant temperature is greater than a predetermined model when the failing index is greater than zero. 